My Number One Hero-(All Might/ Toshinori Yagi) Book 3

21

Warning⚠️ : This chapter is educational

"Pleasure...is the motivation that drives the choices that animals make." you started, "In the human brain that's what beauty is ...pleasure."

"What does pleasure have to do with biology?" Iida asked curiously.

"Glad you asked," I started, "Our view is that the combined activation of visual cortex, orbitofrontal cortex, and nucleus accumbens is the biological signature of our response to beauty."

"I am getting pleasure just from watching you teach," Mineta mumbled.

I rolled my eyes at his perverted behavior and scanned the rest of the class. It was funny how they all held this confused face causing me to laugh and turn around towards the board and sketch an image---an eye.

"Okay, lets break it down to a much simpler topic," I stated, "You guys are looking at me as I give you a lecture about how your brain responds to signals. The very fact that you guys are watching me at the board is your brain sending signals. We humans rely on our senses of sight more than a lot of other animals. A cat can easily find its way in the dark thanks to its sensitive whiskers, but if you try closing your eyes and trying to find your way from your desk to the office kitchen, you'll probably hurt yourself (or others). The smell of microwavable entrees doesn't guide you with precision, nor can you pinpoint the sounds of conversation accurately enough to keep you from running into the wall outside. We perceive the world largely through our eyes.

Still, our eyes are still limited in the grand scheme of things; they can perceive only a tiny fraction of the light that makes up the full electromagnetic spectrum. We can't see x-rays or microwaves; we can only see the light that has wavelengths within what's known as the visible spectrum. The longer wavelengths of the visible spectrum produce red light, and the shorter wavelengths produce purple light. If you've ever seen a rainbow or light that's been passed through a prism, you've seen the full range of the visible spectrum in order from longest to shortest wavelength.

So we've talked a lot about what our eyes perceive; now let's take a closer look at how our eyes take in light and give us the world of images and color we're used to seeing.

Light first passes through the cornea, the outermost part of our eyeball, where it begins to be focused. The cornea, the front transparent layer of the eye, along with the crystalline lens, refract (bend) light to focus the image on the retina. After passing through the cornea, light passes through the aqueous humour, which connects the cornea to the lens. This clear gelatinous mass also provides the corneal epithelium with nutrients and helps maintain the convex shape of the cornea. The iris, which is visible as the colored part of the eye, is a circular muscular ring lying between the lens and the aqueous humor that regulates the amount of light entering the eye. Light passes through the center of the iris, the pupil, which actively adjusts its size to maintain a constant level of light entering the eye. In conditions of high ambient light, the iris contracts, reducing the size of the pupil. In conditions of low light, the iris relaxes and the pupil enlarges.

The main function of the lens is to focus light on the retina and fovea centralis. The lens is a transparent, convex structure located behind the cornea. On the other side of the lens is the vitreous humor, which lets light through without refraction, maintains the shape of the eye, and suspends the delicate lens. The lens focuses and re-focuses light as the eye rests on near and far objects in the visual field. The lens is operated by muscles that stretch it flat or allow it to thicken, changing the focal length of light coming through to focus it sharply on the retina. With age comes the loss of the flexibility of the lens; a form of farsightedness called presbyopia results. Presbyopia occurs because the image focuses behind the retina. It is a deficit similar to a different type of farsightedness, hyperopia, caused by an eyeball that is too short. For both defects, images in the distance are clear, but images nearby are blurry. Myopia (nearsightedness) occurs when an eyeball is elongated and the image focus falls in front of the retina. In this case, images in the distance are blurry, but images nearby are clear.